Modeling of natural radiation annealing in zircon

• Grant number: 21/14361-1
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: March 01, 2022
• End date: February 29, 2024
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geophysics
• Principal Investigator: Sandro Guedes de Oliveira
• Grantee: Giovana Chan Kuang
• Host Institution: Instituto de Física Gleb Wataghin (IFGW). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

Thermochronological methods such as U-Th/He and Fission Track Thermochronology (FTT) are based on the radioactive decay of uranium and thorium isotopes and the radioactive chains initiated in these isotopes. The U-Th/He is based on the accumulation of He, resulting from the alpha decays of this chain, while the FTT is based on the accumulation of tracks (defect trails), caused by the interaction of fragments emitted during the spontaneous fission of U-238. The recoil nuclei in the alpha decays of the natural radioactive series also interact significantly with the crystal structure, giving rise to defects and, mainly in zircon, causing significant structural changes. Both U-Th/He and FTT dating are affected by these structural modifications. The situation is complicated when the defects caused by alpha recoils experience the process of annealing (restoration of the network by heating). Therefore, for the correct interpretation of ages and thermal histories obtained by U-Th/He and FTT, the annealing kinetics of these defects must be modeled. There are still no suitable models in the literature. Based on data on the annealing of defects found in the literature, annealing models will be adjusted and analyzed. The goal is to find one or more models that fit well the laboratory data and provide consistent geological extrapolations. As a tool to carry out this work, a code in R language, which is originally based on Functional Programming, will be adapted for Object-Oriented Programming. With that, the computational tool can be used, in the future, in different contexts.(AU)